Lichen striatus

blaschkitis · linear lichenoid dermatosis

A single line of small papules running down a child's limb along the lines of Blaschko - self-resolving over months, and a diagnosis made entirely from its shape.

DISCHARGEBand B

Recognise

On light skin

Small pink or skin-coloured flat-topped papules, sometimes slightly scaly, coalescing into a narrow band. Erythematous in about 70% of reported cases.

On brown and black skin

The hypopigmented form matters far more here. Around a quarter of reported cases are hypopigmented rather than erythematous, and on brown and black skin a hypopigmented Blaschko line is strikingly visible - frequently the presenting complaint, and frequently mistaken for vitiligo or for a fungal infection. Two practical consequences. First, in darker skin this condition may present as a pale line rather than a pink one, so do not wait to see redness. Second, the pigmentary change commonly outlasts the papules by many months, which is pigment lability rather than persistent disease, and families need telling that clearly or they will return repeatedly for a line that is already resolving. The line itself - unilateral, following Blaschko, not crossing the midline - is tone-independent and is the diagnosis.

In any skin tone

A linear band along the lines of Blaschko - this is the diagnosis and nothing else looks quite like it
Unilateral, and does not cross the midline
The child is well and the line is usually asymptomatic, or only mildly itchy
Diagnosed clinically in around 80% of reported cases - biopsy is rarely needed
Nail involvement can occur where the band reaches a digit
Mean duration about 9.5 months, and treatment was used in only 20% of reported cases

Distribution

A single linear band following the lines of Blaschko, usually unilateral, most often down a limb and occasionally on the face or trunk. The line does not follow a dermatome and does not cross the midline. Mean age 3.8 years in a review of 440 patients, with a female predominance of about 2:1.

Photographs

Lichen striatus on brown skin, showing the pigmentary change that is the presenting complaint in darker skin - a band of altered colour and — Lichen striatus on brown skin, showing **the pigmentary change that is the presenting complaint in darker skin** - a band of altered colour and fine scale rather than the pink papules described in pale skin. **Be aware of what this view does not show well**: the sharp linearity along a line of Blaschko, which is the actual diagnostic feature, is only partly evident here. Trace the lesion on the patient rather than matching it to this photograph.
Fitzpatrick V (Fitzpatrick type estimated from the photograph, not stated by the source) · Mohammad2018 · Wikimedia Commons - Lichen striatus new image.jpg · CC BY-SA 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Lichen planus — Linear lichen planus also follows Blaschko lines but is intensely itchy, violaceous and far more persistent, and is a disease of adults more than children
Psoriasis, including guttate — Linear psoriasis also forms bands, but with thick silvery scale and a typical course elsewhere on the body
Vitiligo — The one families fear. Segmental vitiligo is depigmented - completely white - while lichen striatus is hypopigmented, retains some pigment, and resolves
Tinea corporis, cruris and pedis — Also scaly and asymmetrical and often treated as such; tinea is annular with an active edge, not a Blaschko line
Contact dermatitis - allergic and irritant — Also linear - a plant or a dribble of something - but acutely inflamed, itchy and matching a plausible contact rather than an embryological line

What to do in the ED

Make the diagnosis from the shape. Trace the line - if it runs down a limb, stays on one side and does not cross the midline, and the child is well, the diagnosis is usually this
Do not prescribe an antifungal, which is the commonest wrong treatment here
Reassure actively, with a timescale: resolution averages about nine and a half months, and most reported cases were never treated at all
Warn about the pigmentary tail. The pale or dark line left behind can persist for many months after the papules have gone, especially in darker skin, and is not the condition continuing
Offer a short course of a topical corticosteroid or emollient only if it is itchy; otherwise treat nothing

Disposition

DISCHARGE

Discharge with the diagnosis and the timescale. No investigation and no dermatology referral are needed for a typical case in a well child.

Safety-netting

Return if the line becomes sore, blistered or infected, if it spreads well beyond a single band, or if it has not begun to improve after about a year. The pale or dark mark left behind taking many months to fade is expected and is not a reason to come back.

Sources

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